Oxygen separator and method of generating oxygen

ABSTRACT

The invention relates to an oxygen separator ( 10 ), comprising at least one oxygen separation device ( 12, 14 ) comprising an oxygen separation sorbent ( 16, 18 ) for separating oxygen from an oxygen comprising gas, wherein the oxygen separation device ( 12, 14 ) comprises a gas inlet ( 24, 28 ) at a primary side being connected to an inlet conduct ( 20 ) for guiding a flow of oxygen comprising gas into the oxygen separation device ( 12, 14 ) and having a gas outlet ( 34, 36 ) at a secondary side being connected to an outlet conduct ( 30, 32 ) for guiding a flow of oxygen enriched gas out of the oxygen separation device ( 12, 14 ), wherein the secondary side of the oxygen separation device ( 12, 14 ) is further connected to a source of purging gas for guiding purging gas through the oxygen separation device ( 12, 14 ) and wherein the primary side of the oxygen separation device ( 12, 14 ) is connected to an exhaust conduct ( 70, 72 ) for guiding exhaust gas out of the oxygen separator ( 10 ), wherein the oxygen separator ( 10 ) further comprises a pressure adjusting device ( 40 ) for creating a pressure difference between the primary side and the secondary side of the oxygen separation device ( 12, 14 ), and wherein a gas sensor ( 82 ) is provided in the exhaust conduct ( 70, 72, 73 ) for determining the concentration of at least one component of the exhaust gas. Such an oxygen separator ( 10 ) provides an improved controlling behavior. The invention further relates to a method of generating oxygen from an oxygen comprising gas.

FIELD OF THE INVENTION

The invention relates to the field of oxygen separation. Morespecifically, the invention relates to oxygen separation using pressureswing adsorption for therapeutic applications, particularly in the fieldof home care.

BACKGROUND OF THE INVENTION

Oxygen therapy is the administration of oxygen as a therapeuticmodality. It is widely used for a variety of purposes in both chronicand acute patient care as it is essential for cell metabolism, and inturn, tissue oxygenation is essential for all physiological functions.Oxygen therapy should be used to benefit the patient by increasing thesupply of oxygen to the lungs and thereby increasing the availability ofoxygen to the body tissues, especially when the patient is sufferingfrom hypoxia and/or hypoxemia. Oxygen therapy may be used both inapplications in hospital or in home care. The main home care applicationof oxygen therapy is for patients with severe chronic obstructivepulmonary disease (COPD).

Oxygen may be administered in a number of ways. A preferable way ofoxygen administration is by using a so called on demand generation ofoxygen. Referring to this, commercial solutions, so-called oxygenconcentrators or separators, respectively, are widely known. Theseoxygen concentrators mostly separate oxygen from an oxygen comprisinggas, so that the oxygen is provided on demand, i.e. directly before use.

Known from U.S. Pat. No. 7,329,304 B2 is a portable oxygen concentratorand in detail a portable pressure swing adsorption system forconcentrating oxygen as well as a method for using such an apparatus.Such an apparatus includes a plurality of sieve beds or tanks, acompressor, a lower or air manifold defining a plurality of passagestherein, a storage tank or reservoir, a set of air control valves forcreating one or more flow paths through the passages within the airmanifold, and an upper or oxygen delivery manifold. Further an oxygensensor is provided downstream the reservoir. The oxygen sensor may becoupled to a controller and may generate electrical signals proportionalto the purity that may be processed by the controller and used tocontrol or change operation of the apparatus.

There is, however, still potential for improving the operatingconditions of oxygen separation devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an oxygen separatorand a method of separating oxygen from an oxygen comprising gas which iscost-saving to build, easy to perform, and/or which is advantageous withrespect to controlling oxygen purity.

This object is achieved by an oxygen separator according to claim 1.This object is furthermore achieved by a method of separating oxygenfrom an oxygen comprising gas according to claim 7. Preferredembodiments are defined in the dependent claims.

An oxygen separator for generating a flow of oxygen enriched gas,comprises at least one oxygen separation device for separating oxygenfrom an oxygen comprising gas, wherein the oxygen separation device isconnected to an exhaust conduct for guiding exhaust gas out of theoxygen separator, and wherein a gas sensor is provided in the exhaustconduct for determining the concentration of at least one component ofthe exhaust gas and a control device for controlling the oxygenseparator based on data determined by the gas sensor .

The term oxygen separator as used herein may particularly refer to adevice which is capable of separating oxygen from an oxygen comprisinggas. Consequently, by means of an oxygen separator, starting from anoxygen comprising gas, pure or essentially pure oxygen or at leastoxygen enriched gas may be generated.

The term oxygen separation device may particularly refer to the activepart of the oxygen separator. It may for example comprise an oxygenseparation sorbent which may interact with an oxygen comprising gas, orwith defined constituents of the latter, and may thus separate oxygenfrom the oxygen comprising gas by means of interaction with at least oneconstituent of the oxygen comprising gas apart from oxygen.Consequently, the oxygen separation device as such, or its oxygenseparation sorbent, respectively, is capable of separating oxygen froman oxygen comprising gas particularly by sorption processes, such asadsorption processes. It may thus be designed as an adsorber bed.

Furthermore, the term primary side of the oxygen separation device, asused herein, may refer to the side or the part of the oxygen separationdevice being directed towards the direction, at which the oxygencomprising gas is guided to the oxygen separation device, whereas theterm secondary side of the oxygen separation device, as used herein, mayrefer to the side or the part of the oxygen separation device beingdirected towards the opposite side, i.e. to the side at which thegenerated pure oxygen or oxygen enriched gas is present and guided tothe desired application.

Additionally, the term oxygen comprising gas, as used herein, may referto any gas which at least partly comprises gaseous oxygen, or whichconsists of oxygen. The term oxygen enriched gas shall therebyparticularly mean a gas which has a higher concentration with respect tooxygen compared to the oxygen comprising gas and which may in an extremecase be pure oxygen.

The term pressure adjusting device may refer to any device which iscapable of generating a pressure difference between the primary side andthe secondary side of the oxygen separation device. It may for examplebe a gas compression device being connected to the primary side of theoxygen separation device, or a vacuum pump being connected to thesecondary side of the oxygen separation device.

An oxygen separation sorbent may furthermore be understood as a materialwhich sorbs and thus adsorbs or absorbs at least one substance from theoxygen comprising gas except oxygen much better than oxygen and thuslets oxygen pass at least in a big amount.

The term purging gas according to the present invention shall furtherrefer to a gas which is usable for purging the oxygen separation device,or its oxygen separation sorbent, respectively, in order to desorbadsorbed substances and thus for regeneration purposes. For example,purging gas may be the oxygen enriched gas being produced by the oxygenseparation devices.

The term exhaust gas shall further refer to the gas flowing out of theoxygen separation device in case it is in a purging state. Exhaust gasmay thus particularly be “used” purging gas.

In an exemplary embodiment the oxygen separator may comprise at leastone oxygen separation device comprising, for example, an oxygenseparation sorbent for separating oxygen from an oxygen comprising gas.The oxygen separation device may be equipped with a gas inlet at aprimary side being connected to an inlet conduct for guiding a flow ofoxygen comprising gas into the oxygen separation device and with a gasoutlet at a secondary side being connected to an outlet conduct forguiding a flow of oxygen enriched gas out of the oxygen separationdevice. The secondary side of the oxygen separation device may furtherbe connected to a source of purging gas for guiding purging gas throughthe oxygen separation device and the primary side of the oxygenseparation device may be connected to an exhaust conduct for guidingexhaust gas out of the oxygen separator. Apart from that, the oxygenseparator may further comprise a gas conveying device for generating aflow of oxygen comprising gas into the oxygen separation device and forgenerating a flow of oxygen enriched gas out of the oxygen separationdevice. For example, the gas conveying device may in an example be apressure adjusting device for creating a pressure difference between theprimary side and the secondary side of the oxygen separation device.

An oxygen separator like described above provides improved oxygenseparation purity and a more effective and faster controlling regardingadjustment to altering operation conditions.

In order to achieve this, an oxygen separator like defined abovecomprises at least one oxygen separation device. It may thus compriseonly one oxygen separation device or a plurality of more than one oxygenseparation devices. For example, the oxygen separation device maycomprise two oxygen separation devices and may thus generally form apressure swing adsorption system (PSA system). However, the oxygenseparator may as well form a vacuum swing adsorption system (VSA) or avacuum pressure swing adsorption system (VPSA).

For separation purposes and in an exemplary embodiment, an oxygenseparation device comprises, or is filled with, respectively, an oxygenseparation sorbent for separating oxygen from an oxygen comprising gas.Thus, the oxygen separation device may form a sieve bed. The oxygenseparation sorbent is thereby capable of separating oxygen from anoxygen comprising by sorbing at least one component of the oxygencomprising gas apart from oxygen or at least better than oxygen. Thisfeature is in accordance with the general setup of a pressure swingadsorption system according to which a separation sorbent interacts withat least one component of the oxygen comprising gas with the exceptionof oxygen or better than oxygen and thus lets oxygen pass. This featureallows for at least temporarily immobilizing one or more components ofthe oxygen comprising gas resulting in a separation of oxygen fromfurther components of the oxygen comprising gas. For example, the oxygenseparation sorbent may be designed for adsorbing nitrogen but does lessor not interact with oxygen in order to let the oxygen pass through andto generate a flow of pure or essentially pure oxygen, or of oxygenenriched gas, respectively, when guiding a flow of oxygen comprisinggas, such as particularly air, through the latter.

Non limiting examples for oxygen separation sorbents include zeolites,such as sodium or lithium zeolites, for example the sorbent materialbeing purchasable under its name SXSDM from the firm CECA.

In order to guide oxygen comprising gas to the oxygen separation device,the oxygen separation device, especially each oxygen separation devicepresent, comprises a gas inlet at a primary side being connected to aninlet conduct for guiding a flow of oxygen comprising gas into theoxygen separation device and having a gas outlet at a secondary sidebeing connected to an outlet conduct for guiding a flow of oxygenenriched gas out of the oxygen separation device.

The gas flow, in particular the flow of oxygen comprising gas into theoxygen separation device and the flow of oxygen enriched gas out of theoxygen separation device may thereby be reached by providing a gasconveying device such as a pressure adjusting device which creates apressure difference between the primary side and the secondary side ofthe oxygen separation device. The pressure adjusting device may forexample be a compressor being positioned on the primary side of theoxygen separation device, and/or it may be formed as a vacuum pump beingpositioned on the secondary side of the oxygen separation device.

Next to creating a pressure difference between the primary and thesecondary side of the oxygen separation device, the pressure adjustingdevice may thus be useful for conveying the oxygen comprising gas from asource of oxygen comprising gas to the gas inlet, through the oxygenseparation device and the generated oxygen through the outlet conduct toa user. This step is especially performed in case the oxygen separationdevice generates oxygen and is thus in an oxygen separation mode, or ina feed mode, respectively.

It is however known for oxygen separation devices, and their oxygenseparation sorbents, respectively, that after a certain time of usage,the sorbent material has to be regenerated in order to desorb the sorbedmaterials, such as particularly nitrogen. Therefore, it is known tooperate the oxygen separator, or the oxygen separation device,respectively, in a purge mode by conveying a purging gas through theoxygen separation device. Therefore, the secondary side of the oxygenseparation device, for example the gas outlet of the oxygen separationdevice, is preferably connected to a source of purging gas for guidingpurging gas through the oxygen separation device, and the primary sideof the oxygen separation device, for example the gas inlet of the oxygenseparation device, is preferably connected to an exhaust conduct forguiding exhaust gas out of the oxygen separator.

An oxygen separator thus separates an oxygen comprising gas such as airessentially into nitrogen and oxygen in a cyclic mode of operation. In afirst phase of the cycle the oxygen comprising gas is fed as “inflow”into the oxygen separation device at a higher pressure feed, nitrogen iskept such as adsorbed within this device and pure oxygen is collected asoutflowing “product”. In a second phase of the cycle the separationdevice is regenerated, i.e. a purge gas such as a part of the producedoxygen enriched gas, for example, is fed back into the device at a lowerpressure purge and the previously adsorbed nitrogen is released as“exhaust” into the surrounding atmosphere. For example at least twoseparation devices filled with suitable selectively oxygen separationsorbent are used: while one device is in the “feed” phase producingoxygen enriched gas at higher pressure, the other device, being in the“purge” phase at lower pressure, is regenerated with part of the oxygenflow produced by the first device, for example. After a certain timerespectively arranged valves are switched and both devices change theirrole.

A well-known requirement of using oxygen separators is the adaptation ofthe process to varying process conditions, such as ambient temperature,actual demand of oxygen flow and/or status of the individual separationdevices. Therefore, oxygen concentrators may be controlled by anelectronic unit preferably comprising a microcontroller.

Inventors have surprisingly found that by providing a gas sensor in theexhaust conduct for determining the concentration of at least oneparticularly gaseous component of the exhaust gas, the controlling ofthe oxygen separator and thus the purity and quality of the oxygenenriched gas generated may significantly be enhanced.

In detail, an oxygen separator like described above may enable toestimate the flow rates and the oxygen concentrations—averaged over astrictly limited number of phases of the cycle—in all flows, i.e. in“inflow”, “product flow” and “exhaust flow”. In this way a total oxygenbalance can be made up. With such an oxygen balance it is easilypossible to calculate the rate with which the total amount of oxygencontained in the separation device is decreasing or increasing withtime. This change rate of the total amount of “stored” oxygen is animportant diagnostics to control the separation process, i.e. tominimize the needed power input, to avoid “breakthrough” of the nitrogenfront into the “product” stream and/or to avoid fluctuations of theoxygen purity of the product. Furthermore, this diagnostics is muchfaster requiring a time resolution of a limited number of process cyclesthan other process diagnostics for example based on the oxygen contentof the product flow only, since these diagnostic methods usually havereaction times in the order of several or even tens of process cycles.The diagnostics of the oxygen storage in the oxygen separation devicethereby becomes possible due to the fact that even though the respectiveoxygen separation sorbents are designed for interacting with nitrogenand let oxygen pass, for example, a specific amount of oxygen is anyhowstored in the oxygen separation sieve and is thus detectable.

The concentration of the gas in the exhaust flow of an oxygen separatoris thus a more sensitive and faster measure to control the oxygenseparator and thus for example to achieve or to hold a demanded oxygenpurity compared to sensing the gas concentration, or oxygen purity,respectively, at the product flow. A controlling may for example beperformed by a controlling device which is suitable for adjusting theflow rates of respective gas streams, for adjusting the time scale ofthe feed phase and the purge phase, for adjusting the pressuredifference between primary and secondary side, and for further measures.

Further, due to an improved and more effective controlling, an oxygenseparator like described above may provide a significant improvedreliability. This is due to the fact that even in case conditions appearpotentially decreasing the quality of the oxygen enriched gas, or evenjust change the quality resulting in a less defined product stream, thismay be compensated by a quick and effective controlling. The oxygenseparator thus ensures an improved separation behavior even after longtimes of usage.

The above described improved controlling may thereby be realized withoutfurther energy consumption so that the oxygen separator like describedabove is further very energy saving.

An oxygen separator, or oxygen concentrator, respectively like describedabove thus provides improved controlling of the generated oxygenenriched gas and thus an improved reliability. Such an oxygen separatormay particularly be used for medical applications such as home careapplications especially due to the fact that especially for homecareapplications, where no specially trained users are present, and furtherfor medical applications a high reliability and improved oxygen purityis of significant advantage.

According to an embodiment the gas sensor is an oxygen sensor or anitrogen sensor. Regarding the provision of an oxygen sensor, a veryeasy and direct analysis of the measurement results may be achieved.Further, this embodiment directly allows generating data correspondingto the compound of which information is desired, i.e. oxygen. Negativeinfluences potentially affecting the analysis of the measurement resultsleading to decreased quality of the measurements may be prevented.Regarding the use of a nitrogen sensor, this may be advantageous due tothe fact that the concentration of nitrogen is comparably high, forexample, in case air is used as oxygen comprising gas.

According to a further embodiment at least one further meter is providedin an inlet conduct or in an outlet conduct. For example, such a metermay be a gas sensor or a flow meter or the like. According to thisembodiment, the controlling of the oxygen separator may be conductedeven more effective and precise. In detail by combining a meter in anexhaust conduct together with a gas sensor in an inlet conduct and/or inthe outlet conduct, not only trends or relative changes of the qualityof the generated oxygen enriched gas may be determined, but furtherexact and objective values may be determined. Further, a securitybenefit may be achieved due to the fact that even in case one gas sensorfails, or provides non-correct data, a general controlling may still bepossible by using the further meters, such as gas sensors.

According to a further embodiment the oxygen separator is formed as aportable device. This may be realized, for example, by arranging it intoa portable bag or the like being equipped with an energy source, forexample. Essentially, according to the invention, portable could mean afully independent and self-contained embodiment. Such an embodiment inturn means that no connections, such as to a power source or to a sourceof oxygen comprising gas, are required during use to further componentsnext to the oxygen separator as such. Especially, no connections tostationary elements are required during use and thus during generatingoxygen. Such a portable device may have a grip for carrying it or it maybe arranged in a carrying device, such as a bag. Especially portableoxygen concentrators are sensitive against influences of operatingconditions because of their limited space of the oxygen separationdevice, or the limited amount of oxygen separation material,respectively. For example, with respect to portable oxygenconcentrators, influences such as impurities of the oxygen separationmaterial, altering working temperatures and the like may undercircumstances quickly lead to decreased oxygen selectivity, for example.Consequently, the oxygen separator according to the invention isespecially advantageous for portable devices or for devices comprising asmall oxygen separation device and/or a limited amount of oxygenseparation material.

According to a further embodiment the gas sensor comprises an opticalsensor. Such an optical sensor, for example optical oxygen sensor, maybe usable for detecting gases, such as oxygen, in a very exact mannerthus allowing a very flexible and precise controlling. Further, thesetypes of gas sensors allow a very fast measurement thus allowing thecontrolling to be as well very dynamic. According to this, the qualitysuch as the oxygen concentration of the generated oxygen comprising gasmay as well be improved against a plurality of further sensors. As afurther advantage, an optical sensor may be tailored to the desiredapplication as it may be designed for the desired concentration rangeand may thus provide especially exact measuring results. Apart fromthat, optical sensors may generally be used in liquids as well as ingases resulting in a very stable behavior as far as contaminations areconcerned. As a result, especially an optical gas sensor may provide theadvantages of high precision, high reliability, low power consumption,low cross-sensitivity and fast response timed. As an exemplary andnon-limiting example, an optical sensor may be selective for oxygen andmay be formed from, or may comprise, a device like the “FireSting O2”Fiber-Optic Oxygen Meter being purchasable from the company Pyro ScienceGmbH. This optical sensor, for example, is based on luminescencequenching by O2-interaction.

According to a further embodiment, the control device comprises an inputunit for manually controlling the oxygen separator. According to thisembodiment, the data determined by the gas sensor and/or the furthermeters and for example provided for a user by means of a display may beused for the user to control the oxygen separator manually. Therefore,the user may control via the input device adjust the flow rates ofrespective gas streams, adjust the time scale of the feed phase and thepurge phase, adjust the pressure difference between primary andsecondary side, and further measures.

According to a further embodiment a control unit may be provided beingconnected to at least one of the gas sensor and the at least one furthermeter and may be designed for controlling the oxygen separator based onthe data provided by the at least one gas sensor. The control unit maybe the sole control device or it may be present in addition to the abovedescribed input unit. According to this embodiment, the control unit maybe provided with the data of the gas sensor and/or the further metersand thus with the data of the gas sensor being provided in the exhaustconduct and, in case they are present, with data of further meters suchas exemplarily a gas senor being provided in the product conduct, oroutlet conduct, respectively and/or in the inlet conduct. The controlunit may then automatically control the working of the oxygen separatorlike described above, for example based on stored protocols, or controlinstructions, respectively. This allows a self contained controlling ofthe oxygen separator always providing, inter alia, the best possiblequality of the oxygen enriched gas and the less possible energyconsumption.

With respect to further advantages and technical features of the oxygenseparator it is referred to the description of the method of generatingoxygen, the figures and the description of the figures.

The present invention further refers to a method of separating oxygenfrom an oxygen comprising gas, the method comprising the steps of:performing an oxygen separation step, wherein the oxygen separation stepcomprises guiding an oxygen comprising gas to the primary side of anoxygen separation device, and generating a flow of oxygen through theoxygen separation device by creating a pressure difference between theprimary side and the secondary side of the oxygen separation device;purging the oxygen separation device before or after the oxygenseparation step by guiding a purging gas through the oxygen separationdevice from its secondary side to its primary side and by guidingexhaust gas through the exhaust conduct; determining the concentrationof at least one component in the exhaust conduct; and controlling theoxygen separator based on the determined concentration of at least onecomponent in the exhaust conduct.

A method like described above allows the controlling of the oxygenseparator and thus the purity and quality of the oxygen enriched gasgenerated or the energy consumption, for example, to be significantlyenhanced. Thereby, such a method provides a more sensitive and fastermeasure to achieve or to hold a demanded oxygen purity compared tosensing the gas concentration, or oxygen purity, respectively, at theproduct flow.

In detail, by providing a measure like described above, a total oxygenbalance can be made up. With such an oxygen balance it is easilypossible to calculate the rate with which the total amount of oxygencontained in the separation device is decreasing or increasing withtime. This change rate of the total amount of “stored” oxygen is animportant diagnostics to control the separation process, i.e. tominimize the needed power input, to avoid “breakthrough” of the nitrogenfront into the “product” stream and/or to avoid fluctuations of theoxygen purity of the product.

Therefore, according to a first step, an oxygen separation step isperformed, wherein the oxygen separation step comprises guiding anoxygen comprising gas to the primary side of an oxygen separationdevice, and generating a flow of oxygen through the oxygen separationdevice by creating a pressure difference, for example by a compressor orby a vacuum pump. This step thus corresponds to a generally known oxygenseparation step using an oxygen separator in which an oxygen comprisinggas is guided into an oxygen separation device in which furtherconstituents apart from oxygen are sorbed to an oxygen separationsorbent and oxygen is guided out of the oxygen separation device andfurther to a user.

In order to desorb sorbed substances from an oxygen separation device,or its oxygen separation sorbent, respectively, the oxygen separationdevice is purged before or after the oxygen separation step by guiding apurging gas through the oxygen separation device, and by guiding exhaustgas through the exhaust conduct. This regeneration step may as well beperformed by a gas conveying device such as a compressor or a vacuumpump and is thus a conventional step known from pressure swingadsorption systems, for example.

In order to secure a defined gas quality of the oxygen enriched gas, theconcentration of at least one component and particularly of at least onegas in the exhaust conduct is determined. Further, the oxygen separatoris controlled based on that determined concentration such as gasconcentration. Consequently, the respective gas concentration is usedfor determining an oxygen balance, for example, in order to determine ofthe oxygen separator works in an intended mode or of the process isdeteriorated particularly by influences, such as temperature and thelike. As a result, the oxygen separator is controlled in an improvedmanner allowing an improved quality of the generated oxygen enriched gasthereby requiring a significantly reduced amount of time for such acontrolling.

According to an embodiment the oxygen concentration or the nitrogenconcentration is determined in the exhaust conduct. Regarding themeasurement of an oxygen concentration, a very easy and direct analysisof the measurement results may be achieved. Further, this embodimentdirectly allows generating data corresponding to the compound of whichinformation is desired, i.e. oxygen. Negative influences potentiallyaffecting the analysis of the measurement results leading to decreasedquality of the results may be prevented.

According to a further embodiment the gas concentration of at least onecomponent in the exhaust conduct is measured and averaged over one purgephase. This allows a very dynamic controlling of the oxygen separatordue to the fact that the controlling is based on the measurement resultsof one purge phase only. As a result, negative influences deterioratingthe quality of the oxygen enriched gas may directly be determinedallowing a very effective controlling before significant qualitydecreased may be provided. This further allows a significant securitybenefit especially in case the oxygen separator is used for medicalapplications, for example in the field of homecare. This embodimentthereby becomes possible mainly due to the determination of a gasconcentration in the exhaust gas.

According to a further embodiment it is determined if the oxygenseparation device is in a cyclic steady state for controlling the oxygenseparator. This is a very effective measure for controlling the oxygenseparator having standard conditions and thus already without an erroroccurring. The cyclic steady state may be understood as a situation atwhich the change of the amount of oxygen stored in the oxygen separationsorbent is constant. This is the desired operation of an oxygenseparator and may be described as dν_(O2)/dt=0. In fact, an oxygenseparation device firstly may have a phase at which the amount of oxygenstored in the oxygen separation devices rises after which a cyclicsteady state is reached. Further, a phase may follow at which the amountof oxygen stored falls. Dependent on the status of the oxygen separationdevice, controlling may be advantageous. The determination of thepresent status of the oxygen separation device thereby allows a broadvariety of controlling.

With respect to further advantages and technical features of the methodof generating oxygen it is referred to the description of the oxygenseparator, the figures and the description of the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

In the drawings:

FIG. 1 shows a schematic view of an embodiment of an oxygen separatoraccording to the invention;

FIG. 2 shows a simplified view of a part of a further embodiment of anoxygen separator according to the invention;

FIG. 3 shows a schematic diagram indicating the effect of a changingfeed phase to the oxygen concentration in the exhaust conduct and in theoutlet conduct.

DETAILED DESCRIPTION OF EMBODIMENTS

In FIG. 1, an exemplary embodiment of an oxygen separator 10 forgenerating oxygen is schematically shown. The oxygen separator 10 may beused for generating oxygen with respect to therapeutic applications, forexample in the field of COPD treatment. The oxygen separator 10 may bedesigned as a stationary arrangement, for example for using it in ahospital, or it may be a portable device, for example for using it inthe field of homecare applications. However, the oxygen separator 10 mayfurthermore be used for any application at which pure or essentiallypure oxygen has to be provided, for example in air planes or for weldingpurposes. Such an oxygen concentrator, or oxygen separator 10,respectively, may be based on an oxygen concentrator such as the onecalled SimplyGo and which is purchasable from Philips Respironics.

The oxygen separator 10 according to FIG. 1 comprises at least oneoxygen separation device 12 which is capable of separating oxygen froman oxygen comprising gas. However, it is preferred that the oxygenseparator 10 comprises at least two oxygen separation devices 12, 14being arranged in parallel. In the following, the invention is describedwith respect to two oxygen separation devices 12, 14. However, it isclear for one skilled in the art that every feature may be providedcorrespondingly by using just one oxygen separation device 12 or morethan two oxygen separation devices 12, 14. Each oxygen separation device12, 14 may be formed as a sieve bed and may be equipped with an oxygenseparation sorbent 16, 18. The oxygen separation sorbent 16, 18 isparticularly configured for letting oxygen pass without significantlyimpeding its flow, but for interacting with, or adsorbing, respectivelyother components being present in an oxygen comprising gas. In case airis used as oxygen comprising gas, it is thus preferred that the oxygenseparation sorbent 16, 18 is configured for adsorbing nitrogen. Suitableoxygen separation sorbents 16, 18 may comprises a zeolite material suchas a lithium zeolite material. However it may be possible to use everysuitable oxygen separation sorbent 16, 18 known in the art, for examplefor use in for swing processes, such as pressure swing adsorption orevacuum swing adsorption processes.

An inlet conduct 20 is provided for guiding a flow of oxygen comprisinggas to the gas inlet 24 of the oxygen separation device 12 at itsprimary side. Correspondingly, an inlet conduct 26 is provided forguiding a flow of oxygen comprising gas to the gas inlet 28 of theoxygen separation device 14 at its primary side, respectively.Furthermore, outlet conducts 30, 32 for guiding oxygen enriched gas, orpure oxygen, respectively, out of the oxygen separation devices 12, 14are connected to gas outlets 34, 36 of the respective oxygen separationdevice 12, 14.

The inlet conducts 24, 26 of the oxygen separation devices 12, 14 areconnected to an inlet 38 of the oxygen separator 10. Connected to theinlet 38 is a source of oxygen comprising gas, such as a gas storingdevice or the air surrounding the oxygen separator 10. Additionally, apressure adjusting device 40 for creating a pressure difference betweenthe primary side and the secondary side of the oxygen separation device12, 14 may be provided. According to FIG. 1, the pressure adjustingdevice 40 is formed as a compressor for compressing the oxygencomprising gas and forcing it through the inlet conducts 42, 44, whichmay be part of or connected to the inlet conducts 24, 26, to the oxygenseparation devices 12, 14. Thus, according to the present invention, theexpression an inlet conduct shall mean one, several or all of theseinlet conducts 42, 44, 24, 26. Downstream or upstream the pressureadjusting device 40, an inlet filter 46 may be provided in order toprovide a first cleaning step of the oxygen comprising gas. In detail,especially solid particles may be filtered out of the oxygen comprisinggas.

In order to allow the oxygen comprising gas to be guided through theoxygen separation devices 12, 14 intermittently, inlet valves 48, 50 maybe provided in the inlet conducts 42, 44. A valve according to theinvention shall be any device which may allow a gas flow, inhibit a gasflow and/or regulate the amount of a gas flow. Consequently, by closingthe valve 50 and by opening the valve 48, the oxygen comprising gas maybe guided through the first oxygen separation device 12, whereas theoxygen comprising gas may be guided through the second oxygen separationdevice 14 by opening the valve 50 and by closing the valve 48.Correspondingly, a valve 52, such as a check valve, may be provided inthe outlet conduct 30 and a valve 54, such as a check valve, may beprovided in the outlet conduct 32. By guiding the oxygen comprising gasthrough the first oxygen separation device 12, the valve 52 may beopened whereas the valve 54 may be closed. Correspondingly, by guidingthe oxygen comprising gas through the second oxygen separation device14, the valve 54 may be opened whereas the valve 52 may be closed.

Downstream the valves 52, 54, the outlet conducts 30, 32 are connectedto an oxygen accumulator 56, or a gas tank, respectively, in order tostore the generated oxygen. The oxygen accumulator 56 may be connectedto an outlet conduct 58 in which a flow controller 60 may be provided inorder to control a stream of pure oxygen. Thus, according to the presentinvention, the expression an outlet conduct shall mean one, several orall of these outlet conducts 58, 30, 32. Furthermore, an additionalfilter 62 may be provided in the outlet conduct 58 before the generatedoxygen is guided to an outlet 64. From the outlet 64, the generatedoxygen enriched gas may be guided to the desired application, such as toa patient.

The outlet conduct 30 of the first oxygen separation device 12 and theoutlet conduct 32 of the second oxygen separation device 14 may beconnected by a cross conduct 66 upstream the valves 52, 54, in which aflow regulator 68, such as an orifice or a flow controller, may beprovided. This allows guiding a defined part of the generated oxygen,for example generated in the oxygen separation device 12, 14, backthrough the further oxygen separation device 14, 12, or vice versa, forpurging purposes and thus for regenerating the oxygen separation devices12, 14. Alternatively, the secondary side of the oxygen separationdevices 12, 14 may be connected to a further source of purge gas, suchas a tank comprising oxygen with a high purity, for example, for guidingthe purge gas through the oxygen separation devices 12, 14,respectively. With this regard, exhaust conducts 70, 72 are provided atthe primary sides of the oxygen separation devices 12, 14, eachcomprising a valve 74, 76. If purge gas, such as oxygen enriched gas, isguided through the oxygen separation devices 12, 14, from theirsecondary side to their primary side for regeneration purposes, theoutflow may then be guided selectively through the exhaust conducts 70,72. Further, the exhaust conducts 70, 72 may be guided each to an outletor they may be combined to one common exhaust conduct 73 and may thus beguided to one common exhaust 78.

Furthermore, a heating device 80 for heating the oxygen separationdevice 12, 14 may be provided. The heating device 80 may act on thewhole oxygen separation device 12, 14 or may only heat special regionsfor regeneration purposes. In general, every heating device 80 known inthe art may be used. For example, heating coils may be provided.

In addition, a gas sensor 82, such as an oxygen sensor or a nitrogensensor, for example an optical sensor, is provided in the exhaustconduct 73 for determining the concentration of at least one componentof the exhaust gas. It may be preferred that a gas sensor 82 ispositioned in the common exhaust conduct 73, like shown in FIG. 1, or arespective gas sensor may additionally or alternatively be positioned inthe exhaust conduct 70 of the first oxygen separation device 12 and/orin the exhaust conduct 72 of the second oxygen separation device 14.Moreover and next to the gas sensor 82 positioned in one or more exhaustconducts 70, 72, 73, a meter 84, such as an oxygen sensor or a nitrogensensor or a flow meter may be positioned in one or more inlet conducts42, 44, and a meter 86, such as an oxygen sensor or a nitrogen sensor ora flow meter may be positioned in one or more outlet conducts 30, 32,58, or product conducts, respectively. For controlling the oxygenseparator 10 based on the data provided by the at least one of the gassensor 82 and/or the further meters 84, 86, a control device such as anautomatically working control unit and/or an input unit for manuallycontrolling the oxygen separator may be provided being connected to atleast one of the gas sensor 82 and the further meters 84, 86. Thecontrolling of the oxygen separator is described with respect to thefollowing figures.

FIG. 2 shows a simplified view of a part of an oxygen separator 10according to the invention. In detail, in FIG. 2, in an exemplary andnon limiting manner, the oxygen separation device 12 with its oxygenseparation sorbent 16 is shown. The oxygen separation device 12 again isconnected at its primary side to the inlet conduct 20 and the exhaustconduct 70, according to this embodiment having different connectionpoints, and at its secondary side to the outlet conduct 30 and to afurther purging line 31. By providing a gas sensor 82 in the exhaustconduct 70 and potentially a meter 84 in the inlet conduct 44 and ameter 86 in the outlet conduct 30, a total oxygen balance may becalculated allowing a precise controlling of the oxygen separator 10,and thus of the length of the feed periods and purge periods, of theflow rates of the respective gas streams, of the purity of the oxygencomprising gas etc.

An oxygen separator 10 like described above may enable to estimate, orto determine, respectively, the flow rates and the oxygenconcentrations—averaged over a strictly limited number of phases of thecycle, such as one half cycle and thus one purge phase,—in all flows,i.e. in “inflow”, “product flow” and “exhaust flow”. In this way a totaloxygen balance can be made up. With such an oxygen balance it is easilypossible to calculate, for example, a general tendency as well as theabsolute rate with which the total amount of oxygen contained in theseparation device is decreasing or increasing with time.

For the example that meters 84 and 86 are gas sensors, this can berealized by assuming that the sum of the oxygen in the inflow and thusin the flow of the oxygen comprising gas being directed to the oxygenseparation device 12 during a feed phase and being determined by the gassensor 84, of the product flow and thus of the flow of the oxygenenriched gas leaving the oxygen separation device 12 during a feed phaseand being determined by the gas sensor 86, and of the exhaust flow andthus of the exhaust gas flowing out of the oxygen separation device 12during a purge flow and being determined by the gas sensor 82, isconstant at least in a steady state. This can be measured by therespective gas sensor 82 and the further meters 84, 86, wherein,according to the invention, a gas sensor generally may be understood asa qualitative and further potentially quantitative measuring device ofthe respective gas, or gas streams, respectively. The above may beclarified by the following equation:Φ_(in)yO_(2in)=Φ_(pro)yO_(2pro)+Φ_(ex)yO_(2ex)+dυ_(O2)/dt, whereinΦ_(in) corresponds to the flow rate of the oxygen comprising gas,yO_(2in) corresponds to the oxygen concentration of the oxygencomprising gas, Φ_(pro) corresponds to the flow rate of the oxygenenriched gas (product gas), yO_(2pro) corresponds to the oxygenconcentration of the oxygen enriched gas (product gas), Φ_(ex)corresponds to the flow rate of the exhaust gas, yO_(2ex) corresponds tothe oxygen concentration of the exhaust gas, and dυb_(O2)/dt correspondsto the change of the amount of oxygen stored in the oxygen separationdevice 12, or its oxygen separation sorbent 16, respectively. Thedesired operation of an oxygen separator 10 may be the situation atwhich the cyclic steady state is reached and thus when dυ_(O2)/dt=0. Incase the oxygen concentration in the exhaust flow is measured, such asfor example averaged over half a cycle, or the purge phase,respectively, it can directly be determined, if the oxygen separationdevice works in such a cyclic steady state, or if this preferred stateis lost and measures have to be taken accordingly. This can bevisualized by the following equation describing the oxygen concentrationin the exhaust flow of the cyclic steady state:

yO _(2exCSS)=[Φ_(in) yO _(2in)−Φ_(pro) yO _(2pro)]/Φ_(in)−Φ_(pro)

As a result, by determining the oxygen concentration in the exhaustconduct 70, for example with 0.1% accuracy and using the equationΔyO2_(ex)=yO_(2ex) −yO _(2exCSS) as indicator for the sieve status, thestate of the oxygen separation device may directly be determined. Thismay be performed qualitatively by solely measuring the oxygenconcentration in the exhaust gas or quantitatively by additionallyexamining the further gases like described above.

By knowing the oxygen concentration in the exhaust, an estimation of theflow rate and the oxygen concentration delivered to the user can thusindirectly be calculated. It is possible to infer the total oxygenbalance. By knowing this oxygen balance, it is possible to proceed tothe diagnostic of much faster. This is due to the fact that the purityin the product flow changes very slow due to the “buffer” volume of theoxygen separation device 12.

FIG. 3 further shows a relative evaluation of the state of the oxygenseparation device 14. In detail, in FIG. 3, the oxygen concentration ofthe exhaust gas yO_(2ex), shown as curve A, is shown, together with theoxygen concentration of the oxygen enriched gas (product gas) yO_(2pro)as curve B, against the time. It can be seen that by changing distinctparameters of the oxygen separator 10, a change of the state of theoxygen separation device 12 can be seen by determining the oxygenconcentration of the exhaust gas yO_(2ex) much faster than bydetermining the oxygen concentration of the oxygen enriched gas (productgas) yO_(2pro). In detail, the diagram in FIG. 3 shows the effect to therespective oxygen concentrations in case the feed phase was changed from2.5 s to 3.5 s at 650 s (point a)) and from 3.5 s to 4.0 s at 950 s(point b)). It can clearly be seen that the oxygen concentration in theexhaust gas directly indicates such a change, whereas the oxygenconcentration in the product gas or oxygen enriched gas, respectively,is much slower and significantly less sensitive in indicating such achange in oxygen separation conditions. Thus it is possible to determinevery quickly if, for example, the oxygen separation device 12 works in acyclic steady state, or has an increasing or decreasing amount of oxygenstorage in which case controlling may be triggered in order to improvethe oxygen separation results. This example is thereby especially usefulfor determining trends or tendencies, respectively, of the oxygenseparation device 12 and further clearly demonstrates the very fastcontrolling being possible by a method and an oxygen separator accordingto the invention.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive; theinvention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims. In the claims, the word “comprising” does not excludeother elements or steps, and the indefinite article “a” or “an” does notexclude a plurality. The mere fact that certain measures are recited inmutually different dependent claims does not indicate that a combinationof these measures cannot be used to advantage. Any reference signs inthe claims should not be construed as limiting the scope.

1. Oxygen separator for generating a flow of oxygen-enriched gas,comprising at least one oxygen separation device for separating oxygenfrom an oxygen comprising gas, wherein the oxygen separation device isconnected to an exhaust conduct for guiding exhaust gas comprising usedpurging gas out of the oxygen separator via a primary side of the oxygenseparation device, the primary side being the side at which the oxygencomprising gas is guided into the oxygen separation device, and whereina gas sensor is provided in the exhaust conduct for determining theaverage concentration, over at least one purge phase of the oxygenseparation device, of at least one component of the exhaust gas, and acontrol device for controlling the oxygen separator based on datadetermined by the gas sensor.
 2. Oxygen separator according to claim 1,wherein the gas sensor is an oxygen sensor or a nitrogen sensor. 3.Oxygen separator according to claim 1, wherein at least one furthermeter is provided in an inlet conduct for guiding the flow of oxygencomprising has into the oxygen separation device, or in an outletconduct for guiding the flow of oxygen enriched gas out of a secondaryside of the oxygen separation device, the secondary side being the sideat which the generated oxygen enriched gas is guided out of the oxygenseparation device.
 4. Oxygen separator according to claim 1, wherein theoxygen separator is formed as a portable device.
 5. Oxygen separatoraccording to claim 1, wherein the gas sensor comprises an opticalsensor.
 6. Oxygen separator according to claim 1, wherein the controldevice comprises an input unit for manually controlling the oxygenseparator.
 7. Oxygen separator according to claim 1, wherein a controlunit is provided being connected to at least one of the gas sensor andthe at least one further meter and being designed for controlling theoxygen separator based on the data provided by the at least one gassensor and/or the at least one further meter.
 8. Method of separatingoxygen from an oxygen comprising gas for generating a flow ofoxygen-enriched gas, the method comprising the steps of: performing anoxygen separation step, wherein the oxygen separation step comprisesguiding an oxygen comprising gas to a primary side of an oxygenseparation device, and generating a flow of oxygen through the oxygenseparation device by creating a pressure difference between the primaryside and a secondary side of the oxygen separation device, the secondaryside being the side at which the generated oxygen enriched gas is guidedout of the oxygen separation device; purging the oxygen separationdevice before or after the oxygen separation step by guiding a purginggas through the oxygen separation device from the secondary side to theprimary side and by guiding exhaust gas comprising used purging gasthrough an exhaust conduct; determining the average concentration, overat least one purge phase of the oxygen separation device, of at leastone component of the exhaust gas in the exhaust conduct; and controllingthe oxygen separator based on the determined concentration of at leastone component of the exhaust gas in the exhaust conduct.
 9. Methodaccording to claim 8, wherein the oxygen concentration or the nitrogenconcentration is determined in the exhaust conduct.
 10. Method accordingto claim 8, wherein the gas concentration in the exhaust conduct ismeasured and averaged over one purge phase.
 11. Method according toclaim 8, wherein it is determined if the oxygen separation device is ina cyclic steady state for controlling the oxygen separator, wherein in acyclic steady state of the oxygen separation device the change of theamount of oxygen stored in the oxygen separation sorbent is constant.